um/time: Fixup namespace collision

The new timer_setup() function for struct timer_list collides with a
private um function. Rename it.

Fixes: 686fef928bba ("timer: Prepare to change timer callback argument type")
Signed-off-by: Thomas Gleixner <[e-mail]>
Cc: Richard Weinberger <[e-mail]>
Cc: Jeff Dike <[e-mail]>
Cc: [e-mail]
Cc: Kees Cook <[e-mail]>

arch/um/kernel/time.c

···
 	.flags		= CLOCK_SOURCE_IS_CONTINUOUS,
 };
 
-static void __init timer_setup(void)
+static void __init um_timer_setup(void)
 {
 	int err;
 
···
 void __init time_init(void)
 {
 	timer_set_signal_handler();
-	late_time_init = timer_setup;
+	late_time_init = um_timer_setup;
 }